Numerous polymers and corresponding adhesive compositions have been previously developed which are useful for bonding various surfaces. One particular application in which adhesive compositions are utilized is the injection molding of an elastomeric material onto a metal surface. In this application, an adhesive composition is applied to the metal surface after which the preheated elastomeric material is forced onto the surface of the metal under sufficient pressure. It is important for the adhesive to maintain relative stability with respect to the metal surface during the elastomeric injection process, in order to avoid sweeping of the adhesive which may result in bare spots on the metal surface that will not sufficiently bond with the elastomeric material. In addition to maintaining stability during the injection process, it is desirable for the adhesive to maintain sufficient cohesive strength at elevated temperatures.
One adhesive for bonding vulcanized rubber to metal surfaces is described in U.S. Pat. No. 3,640,941. This adhesive contains a graft polymer formed from the combination of polybutadiene or halogenated polybutadiene and substituted cyclopentadiene monomer, dibasic lead phosphite, resorcinol, and a volatile organic solvent for the graft polymer. Another adhesive composition is disclosed in U.S. Pat. No. 4,795,778 and relates to a Diels-Alder adduct of a chlorinated cyclic conjugated diene and a 1,2-polybutadiene homopolymer having a vinyl content in the range from 88 to 98 percent and a halogen content in the range from 26 to 35 weight percent. The Diels-Alder adduct is utilized in combination with an inert solvent for bonding elastomeric materials.
Many traditional adhesive compositions such as those described above do not maintain sufficient integrity while in contact with the metal surface during injection molding of a hot elastomeric material. Furthermore, many traditional adhesive compositions do not maintain sufficient cohesive strength between the elastomer and metal surface at high temperatures. A need therefore exists for an adhesive composition that would overcome these problems associated with many of the currently available adhesive compositions.